A conventional article of footwear includes two primary elements, an upper and a sole structure. The upper provides a covering for the foot that securely receives and positions the foot with respect to the sole structure. The sole structure is secured to a lower portion of the upper and is positioned between the foot and the ground. The sole structure may attenuate ground reaction forces, provide traction and control foot motions.
The uppers of many articles of footwear, including most articles of athletic footwear, include a forefoot portion and a heel portion. These uppers generally include an opening that may be enlarged to receive a foot and then reduced or tightened to assist in the retention of the article of footwear to the foot. A variety of closure systems are used to enlarge and reduce the foot-receiving opening.
One typical closure system for an upper consists of an elongated opening having laces that may be used to pull together opposing edges of a portion of the elongated opening. Straps or buckles may be used in lieu of laces. Another typical closure system uses one or more elastic gores (or other elastic elements) that stretch during the insertion of the foot into the article of footwear. These closure systems require manipulation by a user, for example, by loosing or tightening the laces or by stretching the elastic, to provide for foot insertion, to provide for foot retention and/or to release the foot.
An example of another type of closure system is described in U.S. Pat. No. 6,189,239 to Gasparovic et al. The shoe includes a forefoot portion and a rear portion that are joined by a flexure member in the midfoot region of the sole. The forefoot portion and the rear portion of the upper are separate assemblies. In order to insert a foot into the shoe, the rear portion of the shoe is flexed downward relative to the forefoot portion, thereby providing an opening for the foot to slide into the forefoot portion. The rear portion of the shoe is then rotated back into alignment with the forefoot portion, thereby enclosing the heel of the foot. A strap is used to connect and secure the upper's heel portion to the upper's forefoot portion. This closure system has the same disadvantage as the above-described closure systems, as it too requires manipulation by a user, for example, by connecting and securing the strap across the rear and forefoot portions, in order to provide for foot insertion, foot retention and/or foot release.
As another example, a shoe is divided into front and back parts which are hinged together at the shoe sole. U.S. Pat. No. 5,481,814 to Spencer discloses that the hinge may comprise a creased part of the sole, preferable the outsole, or a separate mechanical hinge element. Additionally, a spring or a rigid element (with resilient anchoring points) extends across the hinge line to assist in retaining the shoe in the open and in the closed position. The spring or rigid element lies on one side of the hinge line in the open position and lies on the opposite side of the hinge line in the closed position. One disadvantage of this design is the requirement of a fairly long spring or rigid element that is necessary to provide the biasing function. The exposed recess for the spring or rigid element also would tend to collect dirt, mud, or other debris, thereby undesirably increasing the weight of the footwear. These hardware items also may tend to catch on other objects on the ground, thereby causing safety issues.
Although it is recognized that certain articles of footwear, such as clogs, mules, flip-flops, etc., have an opening for receiving the foot that is not enlarged/reduced, these articles of footwear are typically not securely held to the heel of the foot. Thus, these loosely-secured articles of footwear are not suitable for use in situations where the article of footwear must be reliably and securely attached to the foot. Additionally, for many of these loosely-secured articles of footwear, the upper does not include a heel portion.
It would be desirable to provide a closure system for an article of footwear that would not require the use of hands to secure the article of footwear to a foot. Further it would be desirable to provide a closure system that overcomes the disadvantages discussed above.